1. Field of the Invention
This invention relates to a method of magnetic transfer for transferring information to a magnetic recording medium (slave medium) from a master information carrier carrying thereon a magnetic layer pattern representing the information to be transferred to the magnetic recording medium.
2. Description of the Related Art
With an increase in information quantity, there is a demand for a magnetic recording medium which is high in capacity, low in cost and preferably requires a short time to read out a necessary part of data (a magnetic recording medium which allows so-called high-speed access). As an example of such a magnetic recording medium, there has been known a high recording density magnetic medium such as a hard disc or a flexible disc. To realize the high capacity, so-called servo tracking technology for causing a magnetic head to accurately trace narrow data tracks plays an important role. To perform the servo tracking, servo information (a servo tracking signal, an address information signal, a reproduction clock signal and the like) is recorded on the disc as so-called preformat.
As a method of recording the preformat accurately and efficiently, there has been proposed, for instance, in Japanese Unexamined Patent Publication No. 63(1988)-183623, and U.S. Pat. No. 6,347,016, a magnetic transfer method in which a pattern which is formed on a master information carrier and represents servo information is copied to a magnetic recording medium (a slave medium) by magnetic transfer.
In the magnetic transfer, a master information carrier having thereon an irregularity pattern (a pattern of protruding portions and recessed portions) representing information (e.g., servo information) to be transferred to a slave medium (a magnetic recording medium such as a magnetic disc) and a magnetic layer formed at least on the protruding portions is brought into a close contact with the slave medium and a transfer magnetic field is applied to the master information carrier and the slave medium in a close contact with each other, whereby a magnetization pattern corresponding to the information represented by the irregularity pattern is magnetically transferred from the master information carrier to the slave medium. Accordingly, the information carried by the master information carrier can be statically recorded on the slave medium with the relative position between the master information carrier and the slave medium kept constant. Thus, according to the magnetic transfer, the preformat recording can be performed accurately and the time required for the preformat recording is very short.
We, this applicant, have proposed in Japanese Unexamined Patent Publication No. 2001-14667 a method of magnetic transfer in which the magnetic layer of the slave medium is initially magnetized in one direction of the recording tracks and a transfer magnetic layer is applied to the slave medium in the direction opposite to the direction of the initial-magnetization with the slave medium held in close contact with the master information carrier. As the simplest method of applying the initial DC magnetic filed and the transfer magnetic field, there can be conceived a method employing a magnetic field applying apparatus in which a magnetic field is established in an area of the recording track and the slave medium or the slave medium and the master information carrier is rotated relatively to the magnetic field so that a magnetic field is applied over the entire area of the recording track of the slave medium. However, the method using such a magnetic field applying apparatus gives rise to a problem that when rotation of the slave medium is stopped (to end the magnetic transfer) in the magnetic field applied, turbulence of the magnetization is generated due to leakage of the magnetic field in the area of the slave medium to which the magnetic field is applied upon stopping of rotation of the slave medium, which results in noise.